JP3908947B2 - Transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transformer installed in a power system.
[0002]
[Prior art]
The transformer installed in the power system is composed of an iron core and a primary winding and a secondary winding wound around the iron core, and the leakage impedance of the transformer has little effect on the system stability of the installed power system. The leakage impedance value that does not increase the short-circuit current at the time of short-circuiting is specified as a manufacturing specification, and is manufactured to the specified value.
As the value of the transformer's leakage impedance increases, the voltage fluctuation rate increases and affects the stability of the system. Conversely, if the leakage impedance is small, the short-circuit current when the system is short-circuited increases. In addition, an excessive load is mechanically or thermally applied to the devices connected in series to the device, and a value that makes both the voltage fluctuation rate and the short-circuit current appropriate is designated.
[0003]
FIG. 4 is a sectional view of a winding portion of a conventional outer iron type transformer. 1 is an iron core in which silicon steel plates are laminated so as to form a closed magnetic circuit, 2 is a primary winding, 3a and 3b are secondary windings divided on both sides of the primary winding 2. In a transformer, when all the magnetic flux is linked to both the primary and secondary windings, the leakage impedance disappears, but in reality, the magnetic flux linked to the primary winding or secondary winding is lost to the primary and secondary windings. There is a leakage magnetic flux that passes between the secondary windings, and the leakage impedance is determined by the number of turns of the primary and secondary windings and the magnetic resistance of the leakage magnetic path between the primary and secondary windings. The magnetic resistance of the leakage magnetic path is determined by the size and permeability of the leakage magnetic path. In a transformer used in an actual power system, an appropriate leakage corresponding to the short-circuit capacity of the connected power system is required. Designed to be impedance.
[0004]
[Problems to be solved by the invention]
As described above, in the transformer used in the power system, if the leakage impedance during normal operation is small, the voltage fluctuation rate of the power system decreases and the system stability of the power system increases. Short circuit current increases. When the leakage impedance is increased, the short-circuit current can be reduced, but the voltage fluctuation rate increases. The leakage impedance of the transformer used in the power system is such that the voltage fluctuation rate of the connected power system is acceptable, and the short-circuit current when the system is short-circuited is an appropriate value corresponding to the short-circuit capacity of the system. However, if a transformer with a small voltage fluctuation rate and a short-circuit current at the time of a short circuit can be manufactured during steady-state operation of the transformer, the transformer can be reduced in size and weight. However, since current transformers cannot change the size and permeability of the leakage magnetic path, it is not possible to produce a transformer that suppresses the voltage fluctuation rate during normal operation and reduces the short-circuit current during a short circuit. There was a problem that it was not possible.
[0005]
The present invention has been made to solve the above-described problems, and an object of the present invention is to realize a transformer that suppresses the voltage fluctuation rate during normal operation and reduces the short-circuit current during a short circuit.
[0006]
[Means for Solving the Problems]
In the transformer according to claim 1 of the present invention, a magnetic body in which an excitation winding is wound is disposed between the primary winding and the secondary winding, and the magnetic body leaks magnetic flux in a steady operation state of the transformer. Excitation is suppressed so as to be suppressed, and the excitation circuit is controlled to be opened in the event of a short circuit accident.
[0007]
According to a second aspect of the present invention, the magnetic body having the structure of the first aspect is divided into even-numbered units, arranged so that the excitation directions of the magnetic body units are alternately reversed, and the excitation power source Is a direct current power supply, and is configured to control so that the magnetic material is excited to a magnetic saturation state during steady operation and the excitation circuit is opened in the event of a short circuit accident.
[0008]
In the transformer according to claim 3 of the present invention, the excitation power supply having the configuration of claim 1 is an AC power supply, and in steady operation, the transformer is excited in a direction to reduce leakage magnetic flux generated by the primary winding and the secondary winding, and short-circuited. In this configuration, the excitation circuit is controlled to be opened in the event of an accident.
[0009]
The transformer according to claim 4 of the present invention is configured such that the excitation power source of any one of claims 1 to 3 is supplied from its own winding.
[0010]
In the transformer according to claim 5 of the present invention, a magnetic body in which an induction winding is wound is disposed between the primary winding and the secondary winding, and the induction winding suppresses the induced current. A closed circuit is formed in which a reactor and a switch for opening and closing the circuit are connected in series. In a steady operation state, a current that suppresses leakage flux is caused by the induced voltage of the induction winding, and the closed circuit is opened in the event of a short circuit accident It is set as the structure controlled to.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of a winding portion of the transformer according to the first embodiment. In FIG. 1, an iron core 1, a primary winding 2, and secondary windings 3a and 3b are the same as those in FIG. Reference numeral 11 denotes a magnetic body that is disposed between the primary winding 2 and the secondary winding 3a or 3b and serves as a magnetic path for the leakage magnetic flux of the portion, and is divided into even-numbered units and arranged in series. Reference numeral 12 denotes an exciting coil wound around each unit of the magnetic body 11, and reference numeral 15 denotes a DC exciting power source comprising an exciting transformer 15a, a rectifier 15b and a circuit breaker 15c. Excitation coils 12 are wound around the units of the magnetic body 11 and arranged in series, and are arranged so that the excitation directions are alternately reversed.
[0012]
In the transformer configured as described above, in a normal operation state, the magnetic body 11 is excited so as to be magnetically saturated, and the excitation circuit that excites the magnetic body 11 is opened when a short circuit accident occurs. To do.
[0013]
When the magnetization direction of each unit of the magnetic body 11 is magnetized in the same direction, a magnetic flux is generated from the end of the magnetic body 11 toward the iron core 1 of the transformer, and this magnetic flux passes through the iron core 1 of the transformer and is magnetic. The magnetic body 11 is divided into an even number of units, and the magnetization direction of each unit is alternated. By connecting in the opposite direction, both end portions of the magnetic body 11 become the same magnetic pole, and the magnetic flux entering the iron core 1 of the transformer is canceled.
[0014]
The power supplied to the excitation power supply 15 may be supplied from another system, but since excitation is not performed in the case of a short circuit, there is no problem even if it is supplied from its own winding. It will be easy.
[0015]
Thus, when the magnetic body 11 is arranged between the primary winding 2 and the secondary windings 3a and 3b and the magnetic body 11 is excited so as to be in a magnetic saturation state during steady operation, the magnetic body 11 The permeability is small, the leakage impedance of the transformer is reduced, the voltage fluctuation rate can be suppressed, and the magnetic body 11 is increased in permeability when the excitation circuit of the magnetic body 11 is opened at the time of a short-circuit accident. As a result, the short circuit current is suppressed, the voltage fluctuation rate during steady operation is small, and the short circuit current during a short circuit accident is small.
[0016]
Embodiment 2. FIG.
In the first embodiment, the magnetic material is excited by direct current, but in the second embodiment, the exciting winding is excited by alternating current in the direction of demagnetizing the leakage magnetic flux. The configuration is shown in FIG. In the figure, the iron core 1, the primary winding 2, the secondary windings 3a and 3b, and the magnetic body 11 are the same as those in FIG. Reference numeral 22 denotes an excitation winding wound around the magnetic body 11, and reference numeral 25 denotes an AC excitation power source, which includes an excitation transformer 25a and a circuit breaker 25c.
[0017]
This configuration is excited so that a magnetic flux in a direction opposite to the direction of the leakage magnetic flux is generated in a direction in which the leakage magnetic flux between the primary winding 2 and the secondary winding 3a or 3b is reduced during the steady operation of the transformer. In the event of a short circuit accident, control is performed so that the excitation circuit of the magnetic body 11 is opened.
[0018]
When the magnetic body 11 is excited so that the leakage magnetic flux is reduced, in a steady operation state, the leakage impedance between the primary winding 2 and the secondary winding 3a or 3b becomes small, and the excitation circuit is opened in the event of a short circuit accident. Thus, a transformer can be configured in which the leakage impedance is increased and the short-circuit current is reduced.
[0019]
Embodiment 3 FIG.
In the third embodiment, a magnetic body in which an induction winding is wound is disposed between a primary winding and a secondary winding, and leakage flux is suppressed by an induced voltage induced in the induction winding. . The configuration diagram is shown in FIG. In the figure, the iron core 1, the primary winding 2, the secondary windings 3a and 3b, and the magnetic body 11 are the same as those in the first embodiment. 32 is an induction winding wound around the magnetic body 11, and 35 is a current suppression circuit connected to the induction winding 32, in which a current suppression reactor 32a for controlling the induced current during operation and a circuit breaker 35c are connected in series. is there.
[0020]
In this configuration, at the time of steady operation, the current suppression reactor 35a adjusts the current value to an appropriate value by the induced voltage induced in the induction winding 32 by the leaked magnetic flux, and generates a magnetic flux in the direction opposite to the leaked magnetic flux. Adjust to impedance. By controlling so that the current suppression circuit is opened in the event of a short circuit accident, a transformer having a large leakage impedance during steady operation and a small short circuit current during a short circuit accident can be configured.
[0021]
【The invention's effect】
In the transformer according to claim 1 of the present invention, a magnetic body in which an excitation winding is wound is disposed between the primary winding and the secondary winding, and the magnetic body leaks magnetic flux in a steady operation state of the transformer. Since the excitation circuit is opened in the event of a short circuit accident, the leakage impedance is reduced during steady operation and the voltage fluctuation rate is reduced, and the leakage impedance is increased during a short circuit accident, resulting in a short circuit current. Can be configured, and the transformer can be reduced in size and weight.
[0022]
According to a second aspect of the present invention, the magnetic body having the structure according to the first aspect is divided into an even number of units and arranged so that the excitation directions of the magnetic body units are alternately reversed. The power supply is a DC power supply, and the magnetic material is excited to a magnetic saturation state during steady operation, and the excitation circuit is controlled to open in the event of a short circuit, so the leakage impedance is small and the leakage impedance is large during steady operation. A short-circuit current can be kept small, and a transformer with a large adjustment range of the leakage impedance can be obtained by adjusting the excitation current.
[0023]
In the transformer according to claim 3 of the present invention, the excitation power supply having the configuration of claim 1 is an AC power supply, and in steady operation, the transformer is excited in a direction to reduce leakage magnetic flux generated by the primary winding and the secondary winding, and short-circuited. Since the configuration is such that the excitation circuit is opened in the event of an accident, a transformer in which the leakage impedance of the transformer can be easily adjusted can be configured.
[0024]
Since the transformer according to claim 4 of the present invention is configured such that the excitation power supply of any one of claims 1 to 3 is supplied from its own winding, the excitation circuit can be easily configured. can do.
[0025]
In the transformer according to claim 5 of the present invention, a magnetic body in which an induction winding is wound is disposed between the primary winding and the secondary winding, and the induction winding of the magnetic body suppresses the induction current. A closed circuit in which a current suppressing reactor and a circuit breaker that opens and closes the circuit are connected in series is formed, and in a steady operation state, a current that suppresses the leakage magnetic flux is caused by the induced voltage of the induction winding. Since the control is performed so as to open, the leakage impedance can be easily adjusted, and the control circuit can also be configured simply.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a winding portion of a transformer according to a first embodiment.
FIG. 2 is a cross-sectional view of a winding portion of a transformer according to a second embodiment.
FIG. 3 is a cross-sectional view of a winding portion of a transformer according to a third embodiment.
FIG. 4 is a cross section of a winding portion of a conventional transformer.
[Explanation of symbols]
1 iron core, 2 primary coil, 3a, 3b secondary coil, 11 magnetic body,
12 excitation winding, 15 excitation power supply, 22 excitation winding, 25 excitation power supply,
32 induction winding, 35 current suppression circuit.

Claims (5)

In a transformer composed of an iron core and a primary winding and a secondary winding wound around the iron core, a magnetic body in which an excitation winding is wound between the primary winding and the secondary winding. And an excitation power source for exciting the magnetic body, and in a steady operation state of the transformer, the magnetic body is excited so that leakage flux is suppressed, and the excitation power circuit is opened in the event of a short circuit accident. A transformer characterized by controlling. The magnetic material is divided into even-numbered units and arranged so that the excitation directions of each magnetic material unit are alternately reversed. The excitation power supply is a DC power supply. 2. The transformer according to claim 1, wherein the excitation power supply circuit is sometimes controlled to be opened. The excitation power supply is an AC power supply, and is controlled to excite leakage flux generated by the primary and secondary windings during steady operation and to open the excitation power supply circuit in the event of a short circuit accident. Item 1. The transformer according to item 1. The transformer according to any one of claims 1 to 3, wherein the excitation power is supplied from its own winding. A magnetic body in which an induction winding is wound between the primary winding and the secondary winding in a transformer composed of an iron core and a primary winding and a secondary winding wound around the iron core. The induction winding forms a closed circuit in which a current suppression reactor that suppresses the induced current and a circuit breaker that opens and closes the circuit are connected in series. During steady operation, the induction magnetic flux leaks due to the induction voltage of the induction winding. A transformer that controls the current to flow so that the closed circuit is opened in the event of a short circuit accident.

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